This invention relates to manual punch and die sets, in particular, punch and die sets for making washers and the like from sheet material.
Small, portable, punch and die sets long have been used in tool rooms, maintenance shops, and the like, where they are conveniently used for making washers and the like, quickly and inexpensively, from metal, plastic and rubber sheet material. A conventional set includes a die constructed of a steel base block and a clear plastic upper guide block or top plate, secured together and spaced apart a distance sufficient to permit insertion of sheet material in the space between them.
Die openings graduated in diameter are provided by registering openings in the guide block and in the base block, on opposite sides of the space between them. Steel punches having sizes corresponding to the die openings are provided. With a sheet of suitable material inserted between the die blocks, a punch is inserted into one of the openings in the guide block, and then hit with a hammer in the hand of a worker, to severe or to punch out a disc from the material, leaving a corresponding opening in the material.
In making an annular washer or the like having an enclosed opening, the desired opening is provided in the sheet material as a first step. Then, the opening is shifted until it is encompassed by or centered in a larger die opening having a diameter equal to the outside diameter of a desired washer. The centering step is done visually, lining up center lines scribed on the sheet material with permanent center lines on the plastic guide block. The punch corresponding in diameter to the larger die opening is inserted in the opening in the guide block, and then struck with a hammer, to sever a washer from the sheet material, which is ejected beneath the base block.
It is difficult to consistently make washers or the like with accurately oriented or centered holes in them. One reason is that it is difficult to match accurately scribe lines on the sheet material with the center lines marked on the plastic block, in view of the fact that the scribe lines are hidden by the center lines above them. Also, the sheet material may be moved unintentionally after being properly oriented. Consequently, it may be necessary to repeat the procedure to make a satisfactory washer, wasting time and material. Alternatively, the worker may find it necessary to trim an inaccurate washer in some manner, such as by machining off part of the washer when it protrudes undesirably where it is being used.